Trust was being undermined and party loyalty strained by the kind of errors seen over Iraq, she told MPs.

"There is no real collective responsibility because there is no collective - just diktats in favour of increasingly badly thought through policy initiatives
that come from on high", she continued.

Ms Short also complained that she first learnt of the detail of a new UN resolution on rebuilding Iraq from BBC News Online, when her department is supposed to have a key role in the country's reconstruction.

She said the drafting of the resolution had been shrouded in secrecy.

That suggestion was rejected by Foreign Secretary Jack Straw, who said the UN process was open and that the draft resolution would give the UN a "vital role".

Ms Short's replacement is Baroness Amos, the Foreign Office minister who has been the government's spokeswoman on international development in the House of Lords.

'Broken promises'

Ms Short had threatened to quit before the start of war with Iraq, describing Tony Blair as "reckless" during the build-up to military action.

But she decided to stay because she believed leaving when war was unavoidable would be "copping" out.